CHESTERFIELD COUNTY, Va. (WRIC) — More than a dozen people were taken to the hospital after a scary hazmat situation at a neighborhood swimming pool in Chesterfield, Virginia.

Chesterfield Fire and EMS crews responded to a call around 11: 20 a.m. Wednesday said there was a weird smell coming from the Harpers Mill Pool that began to make kids sick.

Parents whose daughters are lifeguards at the pool told Nexstar’s WRIC that their daughters said they saw children vomiting and complaining of sore throats.

A local pool operator told WRIC that the symptoms are telltale signs of chlorine and acid mixing. The chemicals are used in almost every pool but are only safe if done so correctly. The operator said the rare but very serious occurrence can happen as the result of a pump malfunction, leaving victims to breathe in the toxic gas produced from the mix.

WRIC also spoke with a mother, who asked to remain unnamed, who said she was at the pool with five of her kids – aged eight, seven, five, and two years old, and was holding her four-month-old – when they inhaled a “powdery substance” and started choking. The mother said she and her five children went to Chippenham Hospital for treatment, and then returned home.

While on the phone, the mother could be heard still coughing, hours after the incident.

Crews said around 25 to 35 children and adults had to be decontaminated Wednesday and were sprayed down with water to ensure no chemicals had been found on their bodies. Some people had their blood pressure taken and breathing checked as a safety precaution.

Lt. Kenny Mitchell of Chesterfield Fire said most of the complaints were coughing and nausea.

A total of 15 children and one adult were hospitalized with non-life-threatening injuries.

Mitchell said incidents like this tend to occur during this time of the year, towards the beginning of pool season.

“This is pretty common in the summertime with pool chemicals,” Mitchell said. “This time of the year people are mixing chemicals at their homes. This happens a lot at homes as well.”

Mitchell said he has seen chemical mixtures cause this sort of disruption before, but it’s hard to tell at this time what caused the chemical issue. Crews plan to continue the investigation.

Pool management said they plan to do a second assessment of the pool chemicals – separate from those conducted by emergency crews – to make sure there are no more issues.

Management has not set a specific timetable for when the pool will reopen.